Description:
Purpose The purpose of this research was to isolate humic substances and humin from an estuarine sediment core using a novel sequential extraction procedure to characterise the isolates, to determine their compositions and to understand how the organic matter (OM) changes with time. Materials and methods The sediments were exhaustively extracted using the following media: 0.1 M NaOH; 0.1 M NaOH + 6 M urea; and dimethylsulphoxide (DMSO) + H2SO4 (94:6 v/v). Pyrolysis gas chromatography mass spectroscopy (pyGC/MS), and nuclear magnetic resonance (NMR) spectroscopy were the analytical tools that gave the most significant data for the characterisation of the organic isolates. Results and discussion The results indicate subtle molecular compositional differences in relation to the alkaline and alkaline-urea isolates. The humic acids (HAs) and fulvic acids (FAs) are readily solvated in aqueous alkaline media compared to the aqueous insoluble hydrophobic humin (HU) components. In addition to aliphatic hydrocarbons, peptide materials make considerable contributions to the component structures of the isolates. Aryl and O-aryl C units characteristic of lignin, and of cutan structures from plants, indicate contributions from terrestrial OM to the organic components in the HU, especially from the base of the core. The evidence suggests that components of terrestrial plant materials and of microbial biomass are preferentially preserved with time and make the major contributions to the OM retained over long time scales. The data acquired provide detailed information about the origins, compositions, nature and the associations of the OM in the estuarine sediment core. Such information provides a greater understanding of the role of these organic components in the carbon (C) sink. Conclusions Humic acids and FAs are mineralised with time whereas HU is highly recalcitrant and represents a long-term sink for organic C. Humin is a separate organic entity and does not conform to the definitions of a humic substance. Terrestrial OM is preserved over long time scales in the environment. Protein makes significant contributions to all the organic isolates and its preservation suggests encapsulation in hydrophobic domains, or interactions with clay minerals.
Description:
Abandoned historical gold mining wastes often exist as geographically extensive, unremediated, and poorly contained deposits that contain elevated levels of As and other potentially toxic elements (PTEs). One of the key variables governing human exposure to PTEs in mine waste is particle size. By applying a size-resolved approach to mine waste characterisation, this study reports on the proportions of mine waste relevant to human exposure and mobility, as well as their corresponding PTE concentrations, in four distinct historical mine wastes from the gold province in Central Victoria, Australia. To the best of our knowledge, such a detailed investigation and comparison of historical mining wastes has not been conducted in this mining-affected region. Mass distribution analysis revealed notable proportions of waste material in the readily ingestible size fraction (aecurrency sign250 A mu m; 36.1-75.6 %) and the dust size fraction (aecurrency sign100 A mu m; 5.9-45.6 %), suggesting a high potential for human exposure and dust mobilisation. Common to all mine waste types were statistically significant inverse trends between particle size and levels of As and Zn. Enrichment of As in the finest investigated size fraction (aecurrency sign53 A mu m) is of particular concern as these particles are highly susceptible to long-distance atmospheric transport. Human populations that reside in the prevailing wind direction from a mine waste deposit may be at risk of As exposure via inhalation and/or ingestion pathways. Enrichment of PTEs in the finer size fractions indicates that human health risk assessments based on bulk contaminant concentrations may underestimate potential exposure intensities.
Description:
There are few studies in Australia on the fauna of granite caves. Britannia Creek Cave is a granite cave heavily used for recreation yet it has never been mapped nor has the cave fauna been documented. We present here the cave system showing eight ecological zones, A to H, which we mapped, each with different light and moisture characteristics. The faunal diversity and composition in each zone is reported using data recorded from three surveys conducted in April, August and October 2015. For all fauna observed, the zone in which it occurred was noted. Taxa were identified to species level or to genus or family where species was unknown. The composition of fauna assemblages was investigated using Multi-Dimensional Scaling (MDS). Three taxa, the Raphidophoridae (cave crickets), Keroplatidae (glowworms) and Araneae (spiders), were most abundant and occurred in all eight zones. Known cave dwellers, such as Arachnocampa (Campara) gippslandensis (glowworm) were observed in small isolated clusters in three zones, C, E and H. The highest number of taxa (7) were present in the transition zone B, followed by zone A (6) and a dark zone F (6). Fewest taxa (2) were present in transition zone D. Because there are few publications on the biology of granite caves in Australia, our data can contribute to determining future conservation and land management priorities, especially in regard to recreational use which we also recorded.
Description:
A major fish kill occurred in the Richmond River estuary in January 2008 due to oxygen depletion following extensive overbank flooding. This paper examines spatial and temporal changes in the chemistry of main channel waters, thereby identifying the primary sources of deoxygenating water. Over 40 km of the mid- to lower estuary main channel was deoxygenated within seven days of the flood peak. Hypoxia was confined to downstream of the confluences with mid-estuary backswamp basins and occurred during the later phase of the flood recession. Water chemistry at key locations in the estuary indicated elevated concentrations of redox sensitive species associated with acid sulfate soils (ASS) during the hypoxic period. Peak concentrations of Fe
Description:
Using a key station approach, statistical downscaling of monthly general circulation model outputs to monthly precipitation, evaporation, minimum temperature and maximum temperature at 17 observation stations located in Victoria, Australia was performed. Using the observations of each predictand, over the period 1950-2010, correlations among all stations were computed. For each predictand, the station which showed the highest number of correlations above 0.80 with other stations was selected as the first key station. The stations that were highly correlated with that key station were considered as the member stations of the first cluster. By employing this same procedure on the remaining stations, the next key station was found. This procedure was performed until all stations were segregated into clusters. Thereafter, using the observations of each predictand, regression equations (inter-station regression relationships) were developed between the key stations and the member stations for each calendar month. The downscaling models at the key stations were developed using reanalysis data as inputs to them. The outputs of HadCM3 pertaining to A2 emission scenario were introduced to these downscaling models to produce projections of the predictands over the period 2000-2099. Then the outputs of these downscaling models were introduced to the inter-station regression relationships to produce projections of predictands at all member stations.
Description:
Reducing the capital cost of post combustion CO2 capture by eliminating flue gas desulfurisation (FGD) pre-treatment, requires management of the amines preferential SO2 absorption. Novel technologies such as CS-Cap restrict the impact of SO2 to only a small fraction of the amine inventory resulting in high sulfate burden amines. Traditional thermal reclamation of these spent absorbents has advantages regarding simplicity, but ranks poorly for industrial ecology around PCC. These amines require low energy regeneration technologies compatible with their physico-chemical properties that also maximise the potential for valorising by-products. This review summarises the sulfur chemistry and outlines several amine reclamation processes. It assesses the status of established and novel regeneration technologies for their applicability to high sulfur loaded amines. Should deep sulfur removal be required, a hybrid approach with initial bulk removal (as product) followed by a polishing step to further reduce sulfur is prospective. A preliminary estimation of the relative cost of using standard reclamation methods for treating Sulfur loaded CS-Cap absorbent revealed the cost would increase due to its higher sulfate burden despite comparable treatment volumes. Research gaps are identified which would enable better comparison between the costs of traditional FGD versus higher reclamation costs for combined capture technologies.
Description:
Fossil fuels are used widely for energy production and are likely to continue to play a major role world wide for many years to come. Much work has been done on the technology for capturing CO2 from gaseous industrial effluent. For large-scale applications like coal or natural gas-fired power plants, using amine solvents to capture post-combustion CO2 is the most mature CO2 capture technology. This technique can be used to retrofit existing plants by treating the flue gas after combustion. This paper details a dynamic mathematical model for the absorber column constructed from first principles. The loss of MEA through oxidative degradation has been quantified here for the first time and this is currently not possible using commercial packages. Reaction rate kinetics have been employed to predict the accumulation of oxidation products which is limited by the incomplete knowledge of the dominant reactions between O2 and MEA. When research has produced more detailed information about the products formed during this oxidation, it can be inserted easily into the model. Validation has been performed using data from the CSIRO PCC pilot plant at AGL Loy Yang. A limited parametric study of the impact of operating conditions on oxidation was performed.
Description:
Exposure studies have linked arsenic (As) ingestion with disease in mining-affected populations; however, inhalation of mine waste dust as a pathway for pulmonary toxicity and systemic absorption has received limited attention. A biologically relevant extractant was used to assess the 24-h lung bioaccessibility of As in dust isolated from four distinct types of historical gold mine wastes common to regional Victoria, Australia. Mine waste particles less than 20 µm in size (PM20) were incubated in a simulated lung fluid containing a major surface-active component found in mammalian lungs, dipalmitoylphosphatidylcholine. The supernatants were extracted, and their As contents measured after 1, 2, 4, 8 and 24 h. The resultant As solubility profiles show rapid dissolution followed by a more modest increasing trend, with between 75 and 82% of the total 24-h bioaccessible As released within the first 8 h. These profiles are consistent with the solubility profile of scorodite, a secondary As-bearing phase detected by X-ray diffraction in one of the investigated waste materials. Compared with similar studies, the cumulative As concentrations released at the 24-h time point were extremely low (range 297 ± 6–3983 ± 396 µg L−1), representing between 0.020 ± 0.002 and 0.036 ± 0.003% of the total As in the PM20.
Description:
A review of the collembolan fauna of the South Shetland Islands is presented. Cryptopygus nanjiensis Yue & Tamura is synonymized with C. antarcticus Willem. A record of Tullbergia mediantarctica Wise from King George Island is considered a misidentification of Tullbergia mixta Wahlgren and Tillieria penai Weiner & Najt, described from the same island, is synonymized with T. mixta. The current fauna stands at eleven species, of which at least three are introduced. A checklist of Collembola currently considered to occur in the South Shetland Islands is supplied with distributional data.